What causes hair to grow on your tongue?

I don't believe it is really hair, but, bacteria and toxins hiding there. She should scrape her tongue. Using a demitasse spoon, a Popsicle stick, a tongue depressor, or your toothbrush. Scrape from back to front 10 to 15 times.

This pretty rare, but I've heard of it being a hormonal problem. If she is having any other issues, ie hot flashes, mood swings, etc. she may want to consult a doctor. Hormone swings can be saaociated to cancerous growths, but there may be a much more simple explaination. Tell her to consider seeking medical expertise.